Just six months ago, South Sudan became the world's newest nation, born out of decades of conflict with its former rulers in the North. The U.S. played a key role in South Sudan's independence. Now, U.S. officials are worried about ethnic violence South Sudan State of Jonglei now, as well as ongoing tensions between the two Sudans.

NPR's Michele Kelemen reports.

MICHELE KELEMEN, BYLINE: U.S. officials still don't really have a handle on the violence that exploded this year in a remote part of South Sudan. But U.S. envoy Princeton Lyman says one thing is clear; from the deadly cattle raiding and ethnic clashes that have forced tens of thousands to flee, the government's reach still weak.

AMBASSADOR PRINCETON LYMAN: There are real fragile points in this society and years of neglect of their basic needs. And the government is going to have to move very, very fast to get a handle on it and not let ethnic politics get in the way, because some of that also contributed to the problem in Jonglei.

KELEMEN: Humanitarian groups are desperately trying to reach people in South Sudan's Jonglei State. Noah Gottschalk, of Oxfam America, says the violence threatens the new nation's plans to develop its agricultural sector.

NOAH GOTTSCHALK: And when you see this type of displacement happening in this short period of time, where you see the challenges cattle keepers are facing, it's really worrying. If this is what the government of South Sudan pins its hopes on, this will need to be addressed.

KELEMEN: The White House announced recently that it's sending five military advisors to help United Nations peacekeepers, who warned of the latest violence but mainly stayed on the sidelines. The Obama administration also cleared a legal hurdle to provide military assistance to South Sudan.

Envoy Princeton Lyman says the goal is to help a former liberation movement that fought for independence, become a real army with civilian oversight.

LYMAN: Right now, we are looking at help to establishing a stronger Ministry of Defense, command and control capability, human rights monitoring and better overall organization. We have no plans underway for lethal assistance to South Sudan.

KELEMEN: One of Lyman's former aides, Cameron Hudson, says the U.S. needs to show more tough love with South Sudan. Hudson is now with the Committee on Conscience at the U.S. Holocaust Memorial Museum. And he's worried about what former rebels now in government might do during this volatile time.

CAMERON HUDSON: The United states and other allied countries, I think, have a real opportunity and a responsibility to keep South Sudan on the right track.

KELEMEN: The U.S. is also worried about the relationship between the two Sudans. The North accuses the South of arming rebels. U.S. envoy Princeton Lyman can't rule that out, though the South denies it's meddling.

LYMAN: There is frustration but the frustration that both countries have failed to establish the kind of relationships, or even any of the basic institutions, for dealing with their bilateral problems. There's almost no communication between the two.

KELEMEN: And now, there are fears of famine in those areas where Sudan has been cracking down on rebel movements.

LYMAN: We have gone to the government. We have gone to countries around the world to say, look, this is a catastrophe but a preventable one, and urged everybody to say to the government of Khartoum you must allow in the United Nations.

KELEMEN: The U.N. Security Council though has been deadlocked on the issue, says Cameron Hudson, the former State Department official.

HUDSON: What China and Russia see is a proxy war that the South is fueling. And so, I think that they're reticent to take really strong action like the U.S. government would like to see, because they think that there isn't just one side involved here. Both sides are at fault.

KELEMEN: And there is another brewing conflict between the two Sudans that the U.S. is trying to manage. They're fighting over their shared oil wealth, and U.S. officials warn if this isn't resolved soon both countries could face a serious financial crisis.

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